November 20, 2007

Demolition of WTC: Let’s not overstate the case, please

On the Truth Action board, we’ve been having an interesting discussion about the evidence for controlled demolition of the WTC buildings, starting on this page.

There is disagreement about how sure we should be about the idea that WTC 1, 2, and 7 were demolished with explosives and/or thermite. Some, including YT, are 100% sure, while others, such as John Doraemi and Nicholas, believe that it’s likely but not 100% proven. I’m in the latter camp, though not to quite the same extent as John and Nicholas. On the next page of the above Truth Action thread, I voiced some of my own opinions about the need for caution in how we present the case for controlled demolition of the WTC buildings. Below, I’ll voice more of my thoughts on this matter.

In my opinion, we shouldn’t be claiming that the WTC buildings definitely were demolished with explosives and/or thermite. Instead, our claim should be that there’s enough evidence for demolition to warrant a serious and truly independent investigation with subpoena power.

Furthermore, we need to be careful about how we argue for the likelihood of demolition. We need to make sure our arguments are sound; otherwise we risk discrediting ourselves.

To me it seems that a lot of people in the 9/11 Truth movement have overstated the case for demolition and have used some faulty arguments (as well as some good arguments) for the likelihood of demolition. Below is my assessment of various arguments that I’ve seen used:

We do have a very solid, simple case for probable controlled demolition of WTC 7. The almost perfectly symmetical, straight-down, vertical collapse of WTC 7 is extremely unlikely otherwise, especially given the asymmetrical damage.

In my opinion, even this is not 100% proof of demolition. Experts have speculated on other maybe-possible hypothetical scenarios, e.g. in The Collapse of Building 7 (PDF) by Arthur Scheuerman, FDNY (Retired).

But the issues for the Twin Towers are much more complex, more quantitative, and more iffy.

By the way, the symmetry argument for WTC 7 cannot be applied directly to WTC 1 and 2, because the collapse of WTC 7 was bottom-up, like most controlled demolitions, whereas the collapses of WTC 1 and 2 were top-down from the impact floors. Furthermore, the collapse of WTC 2 was not nearly as symmetric as the collapse of WTC 7. The top part of WTC 2 did tilt over quite a bit as it began to fall, a fact which, by example, strengthens the symmetry argument for WTC 7.

There may well be some valid symmetry arguments for WTC 1 and 2 too, but they would have to be a bit more subtle.

For an example of what I mean by overstating the case, a lot of folks have claimed that the sheer speed of collapse inherently violates Newton’s laws.

In fact, the towers did not fall with exactly free-fall acceleration. They fell a little bit slower than that.

The question is whether they fell slower enough to be consistent with an alleged purely “natural” collapse. That’s a quantitative question, not one that can be answered with simple hand-waving.

Zdnenek Bazant and other defenders of the official story have claimed that, once the collapse of either of the Twin Towers got going, the resistance of the columns to being shattered was “negligible” compared to the impact of the top part of the building falling on top of them.

If indeed this claim is true, then what should be the expected collapse time? Using my own oversimplified computer model for WTC 1, assuming a top-down collapse starting at the 95th floor, with totally inelastic collisions and no matter being ejected out of the building, I got 10.5 seconds for the time of descent of the collapse front. Adjusting my model to eject about 70% of the mass of each floor outside the building (probably an unrealistically high estimate), I was able to increase the fall time only to 12 seconds.

So, it seems to me that we can’t prove demolition based on collapse times alone. Based on my own calculations, the fall time might be consistent with the official story, if indeed it’s possible that the resistance of the columns to being shattered could be “negligible” compared to the impact of the top part of the building falling on top of them. Is the latter claim plausible? That too is a quantitative question. It can be answered only by people with an in-depth familiarity with the properties of steel, including how steel deforms.

Is it indeed physically possible that, once the collapse got going, the resistance of the columns to being shattered was “negligible” compared to the impact of the top part of the building falling on top of them. Zdnenek Bazant says yes, Gordon Ross says no.

Not having any expertise on the deformation of steel myself, I’m going to take an agnostic wait-and-see attitude on this particular issue for now. Bazant’s hypothesis about the mechanism of collapse seems very unlikely to me, but I don’t have the necessary background to disprove it. As far as I am aware, Gordon Ross is the only person in the Journal of 9/11 Studies crowd who has made a serious effort to refute Bazant’s hypothesis, but I don’t have the necessary background to evaluate all his arguments either. So, all I can do is wait and see what develops.

In the meantime, I will not claim that the towers’ fall times alone prove demolition, or that the collapses “violate laws of physics” merely because of the fall times or the acceleration. And, if you don’t have quantitative knowledge about the deformation properties of steel, then I don’t think you should make that claim either. There are other, better, yet still relatively simple arguments we can make.

(P.S., 11/22/2007: The ensuing discussion, both here and in the Truth Action forum, has made me aware of some important flaws in my computer model. I’ll revise my model later, and will discuss it in more detail in a future post.)

(Further P.S., 11/22/2007: As I’ve said, although I can’t prove it, it does seem to me that Bazant’s hypothesis is unlikely. An intuitive counterargument – admittedly not a proof – is simply to point to the thickness of the core columns, at least in the lower and middle parts of the building, as seen in this construction photo, for example.)

One simplistic argument, which some people mistakenly believe is very sound, even incontrovertible qualitative proof of demolition of the Twin Towers, is just to point to the explosive appearance of the Twin Tower “collapses.” As Richard Gage has shown in his for-the-most-part excellent video presentation, the collapsing towers, with their enormous and explosive-looking dust clouds, look physically a lot more like volcanic eruptions and nuclear blasts than like any previous known building collapses. See also Jim Hoffman’s page about Other Building Collapses.

While the sheer qualitative resemblance to a huge explosion is worth pointing out, it is far from incontrovertible as an argument for the likelihood of demolition with explosives. The problem with it as an alleged proof of demolition is that the “collapses” of the Twin Towers were an utterly unique event, unique in many ways. Never before in the history of the world have any steel frame high-rise buildings anywhere near 110 storeys tall ever collapsed for any reason whatsoever. Therefore, we don’t know what the collapse of such a huge building “should” look like, if it were to collapse due just to airplane impact damage plus fire on upper floors. (Whether the latter is plausible is, of course, questionable on other grounds. For now we’re just exploring the question of what such a collapse “should” look like if it were to happen.) The examples of building collapses given in Richard Gage’s video presentation, and on websites such as Jim Hoffman’s, all involve much smaller buildings of very different construction.

What we can see with our own two eyes is sufficient for evaluating things within our everyday experience, but not sufficient for evaluating things outside our everyday experience. In science, there are many examples of failed generalizations. An example is the Michelson-Morely experiment, which disproved some common-sense beliefs about the speed of light. (Einstein formulated his Special Theory of Relativity in response to the Michelson-Morley experiment.)

Can a gravity-induced collapse cause something to look like it’s exploding? Actually, yes. To give an extreme example, the most powerful explosions known in the universe are supernova explosions, caused by the gravity-induced collapse of a large star which has run out of nuclear fuel. Of course, that’s a ridiculously extreme example, because the Earth’s gravitational force is much, much smaller than that of a collapsing star. But my ridiculously extreme example does illustrate a key point, which is that size matters.

In a commentary on Thomas Eagar’s collapse hypothesis, Jim Hoffman quotes Jeff King as saying:

He implies that the laws of gravitation are somehow not linear, that if a small object of the same proportions (6.5/1 height to base ratio) tends to topple, a much bigger object of the same proportions will not be similarly unstable. A wooden box 1′ square and 6 1/2′ tall has the exact same geometric relations of center of gravity to base as a big steel box 1300′ tall and 208′ on a side. Nothing changes with a change in absolute size, this is the most basic Newtonian physics.

It is true, as Jeff King says, that the geometric relation of center of gravity to base does not change with absolute size. But many other mechanical properties of an object do vary nonlinearly with “absolute size.” In particular, for objects of a given shape, the force of gravity on an object is a nonlinear function of the object’s height. The force of gravity on an object is the object’s weight, which is proportional to its mass, which (for objects of a given density) is proportional to volume, which, in turn, is proportional to the cube of the height.

In many areas of science, “absolute size” does matter. For example, in high school biology I learned that there are reasons why living cells must be microscopic. The bigger something is, the smaller its surface-to-volume ratio (because, for objects of different size but the same shape, the surface area is proportional to the square of a given linear dimension such as its length, whereas the volume is proportional to the cube of the linear dimension). Thus a too-big cell would have a too-small surface-to-volume ratio, so that, for example, the cell could no longer feed itself via osmosis across the cell membrane. Similarly there are reasons why all insects must be small, compared to most vertebrates. A too-big insect would not have the strength to move its too-heavy exoskeleton.

Back to buildings. As I said earlier, for a building with a given aspect ratio, the volume (and hence also the mass) is proportional to the cube of the height. So, whereas a pair of little toy scale models of the Twin Towers clearly would not be capable of crushing themselves, this, in itself, does not prove that the Twin Towers themselves would be incapable of crushing themselves.

It still seems to me unlikely that the Towers could crush themselves as per Bazant’s hypothesis. But this cannot be disproven with a scale model, or by simply referring to the history of collapses of much smaller buildings.

Might a gravity-induced collapse of a very large, massive building (if such a collapse were to occur) look very different from a gravity-induced collapse of a much smaller building? Quite probably, yes. Would it look at least somewhat like the “collapses” of the Twin Towers? We don’t know, because we’ve never seen a collapse of such a tall and heavy building before.

WTC 1 and 2: Focus on the need for a new investigation

In my opinion, regarding the Twin Towers, I think our best bet is to focus on the deficiencies of the investigations thus far.

Many of those deficiencies, which suggest a coverup, have been noted even by many people who do not otherwise dispute the official story. For example, according to Bill Manning, editor-in-chief of Fire Engineering magazine ($elling Out the Investigation, January 4, 2002):

Did they throw away the locked doors from the Triangle Shirtwaist Fire? Did they throw away the gas can used at the Happyland Social Club Fire? Did they cast aside the pressure-regulating valves at the Meridian Plaza Fire? Of course not. But essentially, that’s what they’re doing at the World Trade Center.

For more than three months, structural steel from the World Trade Center has been and continues to be cut up and sold for scrap. Crucial evidence that could answer many questions about high-rise building design practices and performance under fire conditions is on the slow boat to China, perhaps never to be seen again in America until you buy your next car.

Such destruction of evidence shows the astounding ignorance of government officials to the value of a thorough, scientific investigation of the largest fire-induced collapse in world history. I have combed through our national standard for fire investigation, NFPA 921, but nowhere in it does one find an exemption allowing the destruction of evidence for buildings over 10 stories tall.

No. Fire Engineering has good reason to believe that the “official investigation” blessed by FEMA and run by the American Society of Civil Engineers is a half-baked farce that may already have been commandeered by political forces whose primary interests, to put it mildly, lie far afield of full disclosure. Except for the marginal benefit obtained from a three-day, visual walk-through of evidence sites conducted by ASCE investigation committee members- described by one close source as a “tourist trip” – no one’s checking the evidence for anything.

Bill Manning suspected a coverup, not of demolition but of possible deficiencies in the buildings’ construction:

The builders and owners of the World Trade Center property, the Port Authority of New York-New Jersey, a governmental agency that operates in an accountability vacuum beyond the reach of local fire and building codes, has denied charges that the buildings’ fire protection or construction components were substandard but has refused to cooperate with requests for documentation supporting its contentions.

Even so, we can certainly agree with his call for a better investigation and his denunciation of the destruction of evidence.

“Foreknowledge” by NYC officials – a bad argument

Manning’s Fire Engineering article ends with a link to WTC “Investigation”? A Call to Action, which contains a very interesting perspective on 9/11 from the viewpoint of firefighters, including another issue on which many of us in the 9/11 Truth movement may have overstated our case.

This page says that the editors have “always been leery” of the fireproofing used in the WTC and similar buildings: “Why do many firefighters say that they would rather fight a high-rise fire in an old building than in a modern one? Isn’t it because of the level of fire resistance provided?”

For more about this issue, see the September 11 archives page on the Progressive Review site, including a synopsis of a 1976 book by New York City Fire Commissioner John O’Hagan, High Rise Fire and Life Safety, in which O’Hagan worried about the possibility of the Twin Towers collapsing due to fire.

Whether or not these worries were in fact justified on the grounds given, it would seem that the hypothetical possibility of a steel high-rise building collapsing was not totally unheard of among fire fighters or among fire safety experts before 2001.

We can still argue that such a collapse is unlikely, given the WTC buildings’ highly redundant design, and given the history of more-severe and longer-lasting fires in similarly constructed buildings that did not collapse. (For examples, see Jim Hoffman’s page on Other Skyscraper Fires.)

However, city officials’ worries about the possibility of WTC 1 and 2 collapsing, before those collapses occurred, are not evidence of criminal foreknowledge.

Regarding “foreknowledge” of the collapse of WTC 1 and 2, see also 9/11 cops saw collapse coming by Paul H.B. Shin, New York Daily News, June 19th, 2004, as reprinted on the website of the Skyscraper Safety Campaign, which also contains a lot more information about 9/11 from the viewpoint of firefighters and families of victims.

Anyhow, after the FEMA report, there have been other “investigations.” For now I’ll skip over the 9/11 Commission report, which focussed on matters other than the scientific, but about which there have been many complaints too. Let’s look now at some critiques of the NIST report by scientists and engineers in the 9/11 Truth movement.

Kevin Ryan, a chemist and a former executive at Underwriters Laboratories, has made the following critique:

Some people have tried to discredit Ryan’s critique on the grounds that he is a chemist, not a structural engineer. But the issues he raises are ones of basic scientific methodology, not requiring specialized knowledge of structural engineering.

As I said, regarding the Twin Towers, many of the issues are complex and quantitative, having to do with quantities like temperature of fire and strength of steel. That being the case, it’s probably best to emphasize flaws in the NIST report. There are other issues we can talk about, too, but we need to be careful that our arguments are sound.

Some relatively simple points we can make have to do with Steven Jones’s evidence for the use of thermite/thermate. Although he has not conclusively proven his hypothesis, his evidence clearly does show the need for a truly independent investigation, without the conflicts of interest that have plagued all previous official investigations. See his paper Why Indeed Did the World Trade Center Buildings Completely Collapse? (PDF).

His strongest piece of evidence, in my opinion, is the iron-alloy spherules found in WTC dust – not just Jones’s samples, but other samples too. The spherules most likely were formed from molten iron flying through the air. The existence of molten iron, in turn, strongly suggests the presence of an incendiary such as thermite or thermate, because the fires in the WTC buildings were not otherwise hot enough to melt steel.

Another piece of evidence is the mysterious glowing yellow liquid that poured out of a window on the 82nd floor of WTC 2 just before its collapse. (A post by Danse on the Truth Action board contains this photo.) Obviously we can’t know for sure what this stuff was, but Dr. Jones did experimentally rule out a few possibilities other than molten iron. (See Dr. Jones’s paper, and see also Molten What? (PDF) by Jerry Lobdill, May 2007.)

However, as Nicholas pointed out in our discussion on the Truth Action board, most of these testimonies are about molten metal seen in the debris pile long after the collapse. Only one of them referred to “rivers of molten steel” that were encountered immediately after the collapse. So, perhaps this isn’t as strong evidence as the spherules in the dust.

But then again, there’s also the question of how the debris pile fires managed to get so extremely hot without the presence of an incendiary. While one might expect the pile fires to get hotter than the building fires in at least some places, should we expect them to get that much hotter?

The eye-witness testimony about “molten steel” is confirmed by the existence of the so-called “meteorites,” which contained previously molten iron.

One “debunker,” Frank Greening, has speculated that thermite reactions might have occurred spontaneously when the aluminum from the crashed airplanes melted. See his article Aluminum and the World Trade Center Disaster (PDF). This has been answered by Steven Jones in his video presentation. See also the following:

(P.S., 12/9/2007: Another attempt to refute Jones is this page by Henry62, which I might critique sometime later. For now I’ll just note that it, like most attempts to refute Jones’s hypothesis, doesn’t deal with Jones’s strongest evidence, namely the iron spherules, which were found by the U.S. Geological Survey as well as by Jones. The latter is acknowledged even by at least one of the better-informed official-story defenders, e.g. Frank Greening a.k.a. “Apollo20,” in this post in the JREF forum and in another post quoted here. Note that Greening has some disagreements with NIST and refers disparagingly to “NISTians,” but basically supports the official story in other ways, such as by being a co-author of the most recent Bazant paper.)

Let’s look now at some other common arguments for the hypothesis that the Twin Towers were demolished with explosives and/or incendiaries.

“Ready for shipment”? – just not true

One particularly bad argument I’ve seen is the claim that the columns were all cut up into 30-foot pieces, “ready for shipment.”

In fact, there were many bigger pieces. Judy Wood’s Star Wars Beam Weapons paper, despite its on-the-whole wacky thesis, does contain lots of interesting photos of both the collapses and the rubble piles. In some of the photos, observe what Judy Wood calls “wheat chex,” i.e. large pieces of the perimeter wall skeleton, much too big to fit on a truck.

There were indeed a lot of pieces that were approximately 30 feet long too. But we should expect to see these in any case, because the prefabricated perimeter column assemblies were three storeys tall. In a sufficiently forceful “natural” collapse, if such were to occur, one would expect the columns to come apart at the welds between the prefab column assemblies.

My hunch is that thermite and/or explosive charges were placed at or near many of the welds in order to simulate this, or at least to make sure that it happened. But the existence of many 3-storey pieces is not, in and of itself, evidence of demolition as opposed to a “natural” collapse (if indeed a “natural” collapse could be sufficiently forceful).

(P.S., 11/22/2007: A common “debunker” argument against the idea of explosive demolition of the WTC buildings is that it would require a too-huge number of explosive charges to be placed. The fact that the rubble is not “ready for shipment” cuts down on the number of explosive charges that would be needed to produce the observed results.)

WTC 1: Core column failure and demolition

Another bad argument I’ve seen is the claim that the North Tower must have been demolished with explosives because the fall of the roof antenna, just before the rest of the building began to collapse, implies that the core columns failed first, consistent with what we would expect in a controlled demolition.

It is true that, in a controlled demolition, the core columns are broken first. However, if a building’s core columns fail first, this does not, in and of itself, necessarily imply controlled demolition. In the case of the North Tower, it would have been logical to expect the core to fail first anyhow, if indeed the building were to have collapsed due just to the fires and structural damage (which is questionable on other grounds, as noted elsewhere on this page). Why should we expect the core columns to fail first, at least on or near the 95th floor? For the following combination of reasons:

The core columns supported more than 50% of the total weight.

There were a lot fewer core columns than perimeter columns; hence the core columns (especially the core’s outermost columns, which were attached directly to the floors) supported a lot more weight per column than the perimeter columns did.

At least some of the core columns were damaged by the plane crash, resulting in even more weight per remaining column. (The plane crash probably damaged a larger proportion of the core columns than of the perimeter columns.)

The core columns were tapered. Up at the 95th floor, the core columns were not nearly as thick as they were down on the lower floors. On the other hand, the perimeter columns were not tapered; they were as thick as ever at the 95th floor.

(P.S., 11/27/2007: On the other hand, what does seem very suspicious to me is the witness reports I’ve seen about floors failing far lower in the towers than the impact zone (well before the final “collapse,” that is). This suggests to me some sort of non-natural attack on the core columns in lower parts of the towers. Alas, I don’t have these witness testimonies handy at the moment, so I can’t comment yet on how reliable or well-corroborated they are, but I will keep an eye out for them.)

A faulty objection to the “pile driver” hypothesis

Another flawed argument concerns the alleged “pile driver” effect, which Bazant and other defenders of the official story claim to have been the mechanism of ongoing progressive collapse of the Twin Towers. Some people in the 9/11 Truth movement have claimed that “there’s no pile driver” because the top part of the building is in process of disintigrating too.

But this means that the top part of the building is now a descending pile of rubble, much (though not all) of which is still falling on top of the remainder of the building. Given the huge amount of falling matter, the descending rubble pile does not need to be solid in order to have at least somewhat of a “pile driver” effect on whatever it falls on top of. (Imagine a several-ton pile of rocks falling directly on top of your car all at once. While they might not cause as much damage as a falling solid stone wall, they could still cause plenty of damage.)

The fact that the upper part is not in one piece would indeed cause a significant softening of the impact as it hits the lower part. But, to prove that this rules out progressive collapse, one would need to quantify the effect of the softening. And then, one would still need to determine whether there is enough mass, falling fast enough, to cause the observed effects in the observed amount of time, despite the softening. For now, all that can be said is that the failure even to notice – let alone quantify – this softening is a significant error in Bazant’s papers. This error does cast doubt on Bazant’s progressive collapse hypothesis, but, without further quantitative analysis, we can’t be sure whether this error disproves the progressive collapse hypothesis. Alas, I don’t know how to do all the relevant quantitative analysis.

To me it seems prima facieunlikely that Bazant’s “pile driver” could be sufficiently forceful. But it’s an exaggeration to say that there’s no “pile driver.”

(P.S., 12/8/2007: See the comment thread starting here, where, in a debate with “anonanonanon,” I voice what I think may be the beginnings of a solid scientific argument on this matter, although I don’t have all the necessary technical background to flesh it out.)

WTC 1 and 2: Flying perimeter column pieces

Another bad argument is the claim that only an explosion could have sent pieces of the perimeter columns all the way across West Street.

But flying projectiles are consistent with Bazant’s alleged “pile driver” effect. Imagine yourself shattering something with a hammer. Pieces could well go flying out in all directions.

The only question is whether the descending top parts of the towers could have hit the bottom parts hard enough to send pieces out that far. This is yet another quantitative question.

Offhand, to me it doesn’t seem completely implausible that some pieces could have been flung that far, given the height of the towers, compared to the distance the pieces were flung. If indeed Bazant’s “pile driver” could crush the towers (and that’s the big if, of course), then surely it could also send pieces flying all over the place too.

Sounds of explosions heard by witnesses

Some people believe that our best evidence for demolition is the oral histories and other witness testimonies about explosions.

However, as I’ll explain in a future post, many though not all of these testimonies can be explained away in terms of the official story. So, while some of the testimonies are worth quoting, on the whole they’re not nearly as strong evidence for demolition as some people think they are.

One thing that’s worth pointing out about the oral histories is not just the content of the testimonies themselves, but also the reluctance of the New York City government to release them to the public. The New York Times had to get a court order to get the oral histories released. This fact isn’t really evidence for demolition per se, but it does suggest, at the very least, that someone had something to hide, hence another reason why we need a truly independent investigation.

(P.S., 11/23/2007: The witness testimonies are valid counterevidence in the event that anyone tries to claim something along the lines of: “nobody heard or saw explosions; therefore, there were no explosions.”)

(P.S., 11/25/2007: There’s still the question of whether the explosive sounds heard by many witnesses were loud enough that they could possibly be explosions of demolition charges. That’s another one of those pesky quantitative questions.)

The “squibs” – more details needed

Now for a very complicated matter, whose soundness as an argument for demolition I’m not yet sure of: the “squibs.” See the following Journal of 9/11 Studies articles:

One error I notice on some of the above pages: It is argued that the rubble from the disintegrating upper floors cannot act as a “piston” because it is not airtight. Perhaps it can’t act as a full-fledged “piston,” but it does seem to me that a suddenly descending pile of rubble, even if it has lots of holes and is not very compact, still could cause a huge and sudden downward gust of wind. Perhaps it still couldn’t produce enough of a downward gust of wind to cause the effects claimed by defenders of the official story. But how much sudden downward wind could it cause? And what would be the resulting increases in pressure on lower floors? These are quantitative questions. I’m not sure how to answer them. I would encourage those with relevant expertise, on both sides of the debate, to do some computations. (If anyone reading this knows of such computations having already been done, please let me know via a comment.)

Even more sudden gusts of wind could perhaps be produced if the core columns (or at least the outermost core columns, the ones attached directly to the floors) are failing first, before the perimeter columns. In that case, it seems to me that the suddenly tipping floors could force quite a bit of air out of one or more broken windows on a floor lower than where the perimeter columns have failed. Still they might not be able to blow the dust out as fast as has been observed, but that’s another quantitave question. To prove this, one would need to compute just how fast one should expect air to be blown out of a window if, for example, the floor just above the window were suddenly to lose its core-column support.

The above points do not invalidate the other arguments regarding “squibs.” I personally don’t know how to evaluate most of these arguments.

One possibly good defense of the “squibs” idea is the argument that if windows are being blown out on a given floor, all the windows on that floor should break at once, not than just a few of them, so, if dust were being blown out just by air pressure from the collapse, then it should have come out of a lot more windows. I’m not absolutely sure that this argument is valid, but it does seem to me to be prima facie plausible. It is true that when windows are blown out by a fire, typically many windows are broken all at once, not just a few of them.

Anyhow, if one is going to use the “squibs” as an argument for the likelihood of demolition, then one needs to be prepared to answer the obvious counter-hypothesis that the “puffs of dust” are being ejected merely due to pressure from falling debris on higher floors. This can get very complicated. For example, if your answer is that the puffs are being ejected too fast, then you need to be able to estimate how fast they should be ejected if the sole cause were pressure from falling debris on higher floors.

The too-few-windows argument is probably a better defense than the speed argument. The speed argument definitely needs more quantitative analysis. On the other hand, we’ve all seen windows blown out by a fire, and we saw how the dust clouds from the World Trade Center “collapses” broke not only the WTC buildings’ own windows, but also the windows of many other buildings even several blocks away.

However, to be sure that the too-few-windows argument is valid, it would be necessary to check the floor plans of the floors from which the “squibs” were seen bursting. For example, might the windows that ejected the “squibs” be at the ends of corridors leading directly from the elevators? If so, then perhaps that might explain how a gust of dust from one of the elevator shafts could be blown out from only those particular windows and not from the windows of enclosed offices. (I’m assuming that the offices, even if very big, had walls and doors and were not directly open to the elevators.)

Anyhow, whether or not the “squibs” idea is valid on the whole (which I’m not sure of yet), I personally would hesitate to bring it up in street actions or on a pamphlet. It’s just too complicated, requiring a detailed response to an obvious and simple counterargument.

Even if we can’t be 100% sure that the WTC buildings were brought down by controlled demolition, we do have a 100% solid case for the need for a new investigation. Even many people who do not otherwise support the 9/11 Truth movement would agree that we need a new and truly independent investigation.

When a friend of mine committed suicide back in the late 1980’s, her husband was locked out of their apartment for about three months, if I remember correctly, while the police investigated the possibility of foul play. In other words, murder is something that gets investigated even when it’s very doubtful that a murder has even occurred.

We do know for sure that, on 9/11, at least three thousand people were murdered. What many people question is whether all the perpetrators have been correctly identified. Likewise all the means of murder.

Even more people have questioned how and why the planes were allowed to hit their targets, especially the Pentagon. On the latter question, we’ve gotten a series of conflicting stories from the government.

All the official investigations thus far have been conducted by people who either were employed directly by the Bush administration or otherwise had strong ties to the Bush administration. Obviously this is a conflict of interest. We need a new and truly independent investigation, with subpoena power, by a panel without conflicts of interest.

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“Another bad argument concerns the alleged “pile driver” effect, which the official story claims to have been the mechanism of ongoing progressive collapse of the Twin Towers.”

Not true. NIST did not attempt to explain the “progressive collapse” — only Bazant did. He assumed that the upper part of the building remained intact until it reached the base of the building.

Your argument about rubble also acting as a pile driver does not make sense, because in order for kinetic energy to destroy the upper part, which dissipates energy, the lower part has to offer resistance. And of course it would — the building is progressively more massive and the core columns progressively thicker as the building goes down. Bazant’s claim that the upper 10 stories drove down through the much more massive building below is patently absurd. There is no way that what we observed could have occurred without massive energy being added, and whether or not the “collapse” was at free fall speed or not is a red herring. That the building “collapsed” at all proves that it was demolished.

Whether the energy added was explosives, thermite, nukes, DEW or whatever is beside the point, and I’ve long argued that Wood and Jones should have united on this issue rather than give us their thermite v. DEW puppet show. This guy agrees with me that they are staging a puppet show.

His theory is that the columns were squarely broken at their welds, not cut in angles. I’m not supporting this as I don’t know — I’m just explaining what he thinks happened. My agreement with him is about the puppet show.

This paper, on page 3, shows how much more steel was in the lower floors compared to the upper floors each of the bottom 40 floors had 2-15 times as much steel as the top 20 floors. The steel in the bottom 10 floors was 7-15 times as massive as the steel in the upper 1o floors.

You talk aout a “descending rubble pile,” but that’s not what is observed. The upper floors are simply gone early in the process. The only way Seffens of Cambridge in his recent paper was able to explain all this was by assuming the buildings were uniform in mass all the way down, and assuming no lateral expulsion of material. Which means he proved nothing but his model. Material was expelled, and if impact was destroying the upper block and expelling it laterally, then there was no “descending rubble pile.”

“Another bad argument concerns the alleged “pile driver” effect, which the official story claims to have been the mechanism of ongoing progressive collapse of the Twin Towers.”

In view of your objection that NIST doesn’t discuss this, I’ve changed “official story” to “Bazant and other defenders of the official story.”

Your argument about rubble also acting as a pile driver does not make sense, because in order for kinetic energy to destroy the upper part, which dissipates energy, the lower part has to offer resistance. And of course it would — the building is progressively more massive and the core columns progressively thicker as the building goes down.

But, according to Bazant’s hypothesis, the top part gains kinetic energy on the way down, because the descending rubble pile is both gaining in mass and also accelerating.

Bazant’s claim that the upper 10 stories drove down through the much more massive building below

Upper 15 stories to start with, more storeys as it went down.

is patently absurd.

I too think Bazant’s hypothesis is very unlikely, but I’m not prepared to dismiss it as “patently absurd.” My problem is that I don’t know enough about the properties of steel to compute its resistance to buckling (or to breaking at the welds). So I’m taking an agnostic wait-and-see attitude on that whole question for now. I’m not going to accept Bazant’s word for it, but I’m not prepared to prove him wrong, either. Ditto for Gordon Ross, on the other side of that particular argument.

. There is no way that what we observed could have occurred without massive energy being added, and whether or not the “collapse” was at free fall speed or not is a red herring.

No, it’s not a red herring. That difference in acceleration is one of the quantities one would need in order to compute how much energy is needed.

You talk aout a “descending rubble pile,” but that’s not what is observed. The upper floors are simply gone early in the process.

That’s not what I recall seeing.

What does happen all too early in the process is that everything gets hidden within a huge dust cloud, so we can’t really see what’s going on. But, before that happens, the tops of the buildings are not by any means completely gone, although the “collapse” does start with the top part disintegrating bottom-up from the collapse zone.

The only way Seffens of Cambridge in his recent paper was able to explain all this was by assuming the buildings were uniform in mass all the way down, and assuming no lateral expulsion of material. Which means he proved nothing but his model.

Indeed that would obviously be a wrong assumption. He should be challenged to adjust his model to eject varying proportions of the mass.

Material was expelled, and if impact was destroying the upper block and expelling it laterally, then there was no “descending rubble pile.”

Quite a bit of material was indeed expelled laterally. But the question is how much of the matter was expelled laterally, and at what rate. If less that one floor’s worth was expelled per descending floor, then the mass of the descending rubble pile increases on the way down.

Back to your earlier message: You speak of the Jones vs. Wood squabble as “staging a puppet show.” I don’t think they staged anything; I think it far more likely that they had a genuine clash of egos. This sort of squabble happens all the time, both in political groups and in academia.

You make many unsupported assumptions and ignore existing evidence. I’ll follow your post in order, taking one at a time.

WTC 7:

“We do have a very solid, simple case for probable controlled demolition of WTC 7. The almost perfectly symmetical, straight-down, vertical collapse of WTC 7 is extremely unlikely otherwise, especially given the asymmetrical damage.

…

“Nevertheless, in my opinion, the symmetry of collapse is still a solid argument for at least a very strong likelihood of demolition. And this argument has stood the test of time.”

Your statement is merely an unsupported assertion with no evidence to support it. In fact, there is nothing at all surprising that WTC 7 collapsed as it did given the suspected failure mechanism AND the fact that gravity is the governing mechanism. This is no surprise to structural engineers; why do you think otherwise.

Your argument has not in any way stood any test of time. In fact, it failed the moment it was postulated by a bevy of 9/11 conspiracists. None of them have ever produced one single piece of evidence supporting a controlled demolition of any sort, not in the chemical analysis of the dust and debris, nor in any way producing a working, realistic mechanism on how explosives could have been planted, how much was needed, how many people were needed, how could it have been kept secret, plus dozens of other “hows” they never wish to discuss. There is, in fact, absolutely no physical or other evidence of a “controlled demolition.” There is merely the assertion, repeated for six years now, and again by you, that “The almost perfectly symmetical, straight-down, vertical collapse of WTC 7 is extremely unlikely otherwise,…”

Your statement does not constitute evidence. It constitutes a mere claim and reveals a large failure to understand the nature of evidence, the nature of the scientific method, and the apparent willingness to accept uncritically what you think sounds good for something other than establishing the truth.

You go on to assert: “As far as I am aware, no “debunker” has yet refuted it.”

You must be completely unaware that you have absolutely NO evidence to refute! You have just repeated an unsupported assertion. You just have claimed “it looked like a controlled demolition, therefore it was one.” Nothing more, nothing less. You have produced no evidence that can be tested or falsified. You are entitled to your opinion. You most certainly are not entitled to have any assertion you wish to make taken as fact. You are engaging in mere sophistry. Why? What’s the point? How does that possibly serve the truth?

Evidence compounds. You cannot look at WTC 7 and claim an “observation” has no explanation other than what you “think” and add to the mistake by ignoring ALL of the other evidence surrounding the events leading to the collapse. One does not get to assert he or she has special dispensation to choose that evidence which may be “convenient” and ignore that which is inconvenient.

Produce the evidence for controlled demolition. That is what counts. After six years, we are still waiting for any evidence whatsoever of controlled demolition. And we keep waiting. There is nothing for US to refute; it is up to you to prove a case with evidence.

[…] the Screw Loose Change blog, in the comments on Pat Curley’s recent post about me (to which I replied here), the first three comments were as follows: They are blatently going to crucify her. Jon | 11.21.07 […]

“But, according to Bazant’s hypothesis, the top part gains kinetic energy on the way down, because the descending rubble pile is both gaining in mass and also accelerating.”

Restating the tautology does not prove it. And read Bazant’s paper — he claims there was a “crush down phase” and a “crush up phase.” The top 15 stories (10, 15, 20, whatever) remained intact all the way down, crushing through far more massive floors, and not being destroyed upward until they hit the base. This is nonsense. The impact would also act on the falling stories, which are less massive, so they would be crushed. The collapse would have been arrested, assuming it started at all. You can’t overstate the parently obvious. Bazant is a liar, and he knows it.

Your claim that the majority of structural engineers buy this is not supported. Read the Engineering News Record — professional organizations denied this was a “progressive collapse,” because when it came to actually changing building codes based on NIST’s findings, they said “no way.”

Why challenge Seffen? He’s full of it, and he knows it. What a disgrace that the name of Cambridge is attached to this. Same for Northwestern and MIT. Seriously, Diane, it’s time to stop humoring these people. This is not rocket science. We don’t need to model the absurd — Seffen and Bazant have done that.

Of course this doesn’t prove it. I was responding to what appeared to me to be a fallacious objection, but that doesn’t prove it true.

And read Bazant’s paper — he claims there was a “crush down phase” and a “crush up phase.” The top 15 stories (10, 15, 20, whatever) remained intact all the way down, crushing through far more massive floors, and not being destroyed upward until they hit the base. This is nonsense.

Indeed Bazant’s model is, at the very least, a vast oversimplification. The videos show at least a partial “crush up” phase first.

The top 15 stories (10, 15, 20, whatever) remained intact all the way down, crushing through far more massive floors, and not being destroyed upward until they hit the base. This is nonsense. The impact would also act on the falling stories, which are less massive, so they would be crushed. The collapse would have been arrested, assuming it started at all.

It seems likely to me that the collapse would be arrested too. I’m just not prepared to declare that with certainty, though, because there are too many things I don’t know about the properties of steel. For example, I’m not prepared to rule out the possibility that the initial “crush up” phase might create enough downward momentum in the top part to cause some significant downward crushing. If the latter were to happen, then the descending rubble pilw would, at that point, start picking up more mass, thus maybe more momentum. Of course this is all very iffy at best.

Your claim that the majority of structural engineers buy this is not supported. Read the Engineering News Record — professional organizations denied this was a “progressive collapse,” because when it came to actually changing building codes based on NIST’s findings, they said “no way.”

Can you give a more specific citation? I would be very interested to see this. Also, did they deny any kind of “progressive collapse,” or did they they just deny, more specifically, pancaking floors (as opposed to column failure) as the mechanism of progressive collapse? If indeed they denied any kind of “progressive collapse,” did they propose any other mechanism?

Anyhow, I should re-do my computer model to include that initial “crush up” phase.

I’ll look for the article. It’s not online — I printed from Nexis at my university’s library. If I find it I will scan and post at my blog. You might look in Engineering News Record yourself, since you are the one that claimed that the majority of structural engineers endorse the NIST findings.

The engineers did not propose another mechanism — you miss the point. They were denying that NIST’s WTC findings had any relevance to building design. There’s no money in coming up with an alternative mechanism. The point is to make sure that the NIST report is not taken as reality and used to propose new building standards, which presumably would be necessary if buildings could indeed collapse that easily.

I’m not sure what you mean by “that initial ‘crush up’ phase.” In Bazant’s crackpot paper, the “crush up” came last. If there had been an initial crush-up phase, then obviously the collapse would have been arrested.

The fact that the upper part is not in one piece would indeed cause a significant softening of the impact as it hits the lower part. But, to prove that this rules out progressive collapse, one would need to quantify the effect of the softening. And then, one would still need to determine whether there is enough mass, falling fast enough, to cause the observed effects in the observed amount of time, despite the softening. For now, all that can be said is that the failure even to notice – let alone quantify – this softening is a significant error in Bazant’s papers. This error does cast doubt on Bazant’s progressive collapse hypothesis, but, without further quantitative analysis, we can’t be sure whether this error disproves the progressive collapse hypothesis. Alas, I don’t know how to do all the relevant quantitative analysis. (Wording of this paragraph corrected, 11/25/2007.)

The earlier version read:

It seems to me that what matters is the descending rubble pile’s total downward momentum and kinetic energy. The question is whether it contains enough mass, falling fast enough, to cause the observed effects in the observed amount of time. This is a quantitative question, to which I don’t know the answer.

You were more correct the first time. Use physics. A 100 kg piece of steel falls and hits the ground at 5 m/s. Calculate the force exerted on the ground produced by the impact. Now do the same calculation for the same piece of steel hitting the same way, except it broke in two slightly before impact. What if the steel broke in four pieces?

If the steel breaks up into two or more pieces, then there is no longer one single collision when they hit the ground. Instead there are now two or more separate, smaller collisions, one for each piece, unless they all hit the ground at exactly the same instant, which is unlikely.

Try dropping a single little stone on your bare foot, just hard enough to hurt just a little. Then try dropping an equivalent amount of sand on your other foot from the same height. Feel the difference? Even if you first moisten and squeeze the sand, so that it falls as a compact wad, chances are it won’t hurt nearly as much as the stone.

The difference between one single collision and multiple separate collisions (assuming equivalent total amounts of momentum and kinetic energy) would make no difference if the pieces were hitting a free-floating object with no resistance to being moved. In that case, the same amount of momentum would be transferred to the free-floating object regardless of the number of pieces hitting it. On the other hand, if the collision is not with a free-floating object, but with an object to be dislodged or broken, then a sufficiently high instantaneous amount of force is needed.

Diane wrote:
>If the steel breaks up into two or more pieces, then there is no longer one >single collision when they hit the ground. Instead there are now two or >more separate, smaller collisions, one for each piece, unless they all hit >the ground at exactly the same instant, which is unlikely.

Hey, I thought you studied Physics! I am sure you didn’t make that up! Didn’t galileo prove if a single piece broke in two in mid-air that both pieces would hit the ground at the same time? The basic physics certainly tells you that, in paritice their might be a little shift on air resistance, but we are still talking about

Diane wrote:
>Try dropping a single little stone on your bare foot, just hard enough to >hurt just a little. Then try dropping an equivalent amount of sand on your >other foot from the same height. Feel the difference? Even if you first >moisten and squeeze the sand, so that it falls as a compact wad, chances >are it won’t hurt nearly as much as the stone.

On the other hand, if you drop a small dart on your foot, half the weight of the stone, I bet it will hurt like hell and you might even trouble walking for a few days. Why the difference?

Diane:
>The difference between one single collision and multiple separate >collisions (assuming equivalent total amounts of momentum and kinetic >energy) would make no difference if the pieces were hitting a free-floating >object with no resistance to being moved. In that case, the same amount of >momentum would be transferred to the free-floating object regardless of the >number of pieces hitting it. On the other hand, if the collision is not >with a free-floating object, but with an object to be dislodged or broken, >then a sufficiently high instantaneous amount of force is needed.

Well sort of. In both cases the force applied is the same, what’s different is the reaction. In the first case, the reaction all goes to motion, in the second it goes some to motion and some to compress the support as if it were a spring, and if the spring is squeezed too much, into breaking the spring.

Brings us back to the dart. Why does a lightweight dart do the most damage, a rock less, and the sand packet even less. Mainly it has to do with the mass flux (defined as mass/area/time). The small surface area of the dart tip concentrates the entire force in a single point, therefore a small weight does huge damage. Rock is blunter, less concentrated, but heavier, so can still do damage. The sand is the bluntest because the sand itself will deform and spreading out the force over an even larger area.

For the WTC, we know the mass is the same whether it is one piece or many (except that material ejected to the side). The time is the same (or nearly so) for both cases, because Newton’s laws (see Galileo discussion above) of motion say so. Some spreading in time may occur due to air resistance or mid air collisions of the rubble, but looking at videos, it really seems pretty concentrated, and in any event, there is an even larger intact mass of building right behind the main front. Calling this a pile driver is a little misleading, it’s more like an avalanche, with one really really big rock at the top.

In any case, the area that is being struck, is the entire area of the floor. However, the collapse occurs because the columns can no longer hold the required force, so the reactions are transmitted to the columns and concentrated there with the first thing to break mostly the weakest associated points – probably the welds and bolts.

Or, in sum, if you drop a ten pound bag of sand or a ten pound rock on the floor of your building, the reaction at the columns will be almost the same, but the rock may also chip the floor.

Hey, I thought you studied Physics! I am sure you didn’t make that up! Didn’t galileo prove if a single piece broke in two in mid-air that both pieces would hit the ground at the same time?

That would depend how they broke apart. If the thing that broke them apart exerted an upward force on one piece and a downward force on the other piece, then they certainly wouldn’t hit the ground at the same time. Ditto if whatever broke them imparts a change in velocity with even a slight vertical component differing between the two pieces.

Galileo’s experiment involved two objects dropping from exactly the same height, not an object breaking.

Furthermore, in practice it is a challenge to drop two objects at exactly the same time, down to the picosecond. (I’m talking about the difference in start times here.) Assuming equal air resistance, the times that the two objects hit the ground will differ by the same amount as the times they started dropping.

On the other hand, if you drop a small dart on your foot, half the weight of the stone, I bet it will hurt like hell and you might even trouble walking for a few days. Why the difference?

Because the force is concentrated in a smaller area, hence greater pressure.

You’ve given yet another example of how the effect of dropping an object (or a bunch of objects) depends on more than just the total momentum and kinetic energy.

Regarding what I said about one object vs. many pieces, with same total mass:

In both cases the force applied is the same

No, the force is NOT the same. The pre-collision momentum and kinetic energy are the same, but the force isn’t, as I will explain below.

Let’s consider the case of objects hitting the ground, which stops them. By Newton’s third law, the force with which they hit the ground is equal to the force that the ground exerts to stop them. The total impulse, which is the integral of force over time, must be equal to the pre-collision momentum of the falling object(s). Hence the impulse must be the same for the two cases, but not the force. If there’s just one object, or if multiple objects are falling at exactly the same time, then the impulse is distributed over a smaller amount of time than it is if the objects are hitting the ground at slightly different times. Since the impulse is the same in the two cases, less time means more force.

Why does a lightweight dart do the most damage, a rock less, and the sand packet even less. Mainly it has to do with the mass flux (defined as mass/area/time). The small surface area of the dart tip concentrates the entire force in a single point, therefore a small weight does huge damage. Rock is blunter, less concentrated, but heavier, so can still do damage. The sand is the bluntest because the sand itself will deform and spreading out the force over an even larger area.

That is true too.

Some spreading in time may occur due to air resistance or mid air collisions of the rubble, but looking at videos, it really seems pretty concentrated, and in any event, there is an even larger intact mass of building right behind the main front. Calling this a pile driver is a little misleading, it’s more like an avalanche, with one really really big rock at the top.

That’s a reasonable description, yes.

In any case, the area that is being struck, is the entire area of the floor. However, the collapse occurs because the columns can no longer hold the required force, so the reactions are transmitted to the columns and concentrated there with the first thing to break mostly the weakest associated points – probably the welds and bolts.

Or, in sum, if you drop a ten pound bag of sand or a ten pound rock on the floor of your building, the reaction at the columns will be almost the same, but the rock may also chip the floor.

Agreed that the difference would be far less from the point of view of the columns than from the point of view of the floor, but I’m not convinced that the difference from the point of view of the columns would be negligible. It seems to me that the effect of any spreading over area would be negligible for the columns, but not the effect of spreading over time.

And, perhaps I’m mistaken about this, but it does seem to me that there would be enough of a time spread to have a significant effect on the magnitude of the force spike. Of course, it still might not be significant enough to disprove Bazant’s hypothesis.

In any case, Bazant, in his latest paper, talks about a crush-down followed by crush-up. This is inaccurate because, in reality, for the North Tower, there were at least a few storeys’ worth of crush-up before any crush-down started happening. What needs to be determined is whether and to what extent this is a significant error (or at least oversimplification).

“Use physics. A 100 kg piece of steel falls and hits the ground at 5 m/s. Calculate the force exerted on the ground produced by the impact. Now do the same calculation for the same piece of steel hitting the same way, except it broke in two slightly before impact. What if the steel broke in four pieces?”

Are you considering that the breaking would itself dissipate kinetic energy?

The question we are addressing is whether Bazant considered that the energy of impact would also act on the falling object, and since the object that is purportedly falling is weaker (each floor is slightly less massive) then the upper falling block should break up quickly and no longer act as a hammer driving down through the progressively thicker floors.

“In any case, Bazant, in his latest paper, talks about a crush-down followed by crush-up. This is inaccurate because, in reality, for the North Tower, there were at least a few storeys’ worth of crush-up before any crush-down started happening. What needs to be determined is whether and to what extent this is a significant error (or at least oversimplification).”

The “error” is manifest – it speaks for itself. Bazant’s theory not only does not account for what was observed, it is self-contradictory. Once the crushup starts, why would it stop when it got to higher and weaker floors? Why would the crushed material not be expelled laterally, at least in part, as the building moved down during the crush up stage?

Diane, I don’t disagree with what you are saying here, but I was trying to suggest to you how to quantify your question. I am suggesting you can use a mass flux approach, where the mass hitting a given floor is estimated by looking at how much mass would pass through an imaginary plane sitting an infintesimal distance above the floor and equal in size to the area of the floor. This would give you the amount of material hitting the floor per unit time. You can estimate this by guessing how much a broken up floor might spread as it falls to the floor below.

I also speculated that this wouldn’t make much difference in bazant’s calculations, but you can pretty much ignore that speculation since I haven’t done this calculation myself.

The nice thing about Bazant’s paper is that he gives you an equation that describes everything, and then plugs in calculations to estimate all the parameters. It wouldn’t be hard to alter his model to reflect a difference sequence of crush up and crush down, or different assumptions about the force bearing down on the building etc.

Diane, I’ve not yet been able to find the ENR article, but I can provide a statement of Gene Corley, who ran the FEMA and Oklahoma coverups.

(An aside: I’ve decided to speak with the same conviction of Matthew Rothschild, Alexander Cockburn, Chip Berlet, and Robert Scheer, who use words like “nuts,” “crackpot,” and “inane” to describe 9/11 “conspiracy theories.” The difference is, I have a basis for my conviction because I have addressed the facts. I shall also use this same conviction in addressing Bazant’s patently absurd, and thus fraudulent, “theory.” I think it’s far past time for 9/11 activists to quit being mealy mouthed in their conviction that the buildings were demolished, because it is completely obvious and has been since the morning of 9/11.)

“If you’re going to do something to minimize this type of effect, the right thing to do is invest in security, so that the terrorists don’t get the tools they need to cause this type of an attack.”

This is the basic position of the engineering organizations that gave input to meetings held by NIST to implement NIST’s recommendations. Their position was that the Twin Towers “collapses” were a unique event, and that the real cause was terrorism, so NIST’s recommendations should not be implemented through change in building codes. As part of this, ENR quoted engineers saying that these were not “progressive collapses.” What exactly they mean, I don’t know. They may simply mean that these are not events that they need to plan for.

Now, compare that with what the PBS article says: “In fact, the entire architectural and engineering communities were stunned.” What all this says to me is that the engineering community knows that they do not need to worry about this happening again, so they are against changes in building standards.
If in fact buildings could collapse so easily, they would have to be concerned. I read into this an unstated recognition that the buildings did not collapse as stated. This need not be said in NIST hearings in order to oppose implementation of NIST’s findings, and these industry groups have no interest in saying it. So they don’t. But what they know is that this should not have happened. They were “stunned.” The silence of the many cannot be read as agreement with the findings of government agencies and the likes of Corley and Bazant.

“Are you considering that the breaking would itself dissipate kinetic energy?”

I did not state how the piece broke in two, but assumptions were made anyway, both in my mind and the reader’s mind. I tried to write the question in the manner of an introductory physics exercises, which are purposely simplified to draw out certain principles. In this case, the idea was that the piece spontaneously broke apart (if you need a mechanism, assume it was held together by an unstable type of glue that happened to dissolve away during the fall). Basic theoretical physics say that the two pieces fall together and land simultaneously with the same force as if it were one piece. Real world is more complicated of course. But this is how you do physics and engineering. Start with the most basic theory and add on complications.

dwightvw said:
“The question we are addressing is whether Bazant considered that the energy of impact would also act on the falling object, and since the object that is purportedly falling is weaker (each floor is slightly less massive) then the upper falling block should break up quickly and no longer act as a hammer driving down through the progressively thicker floors.”

Actually, his equations do implicitly include this in the way he handled crushup and crushdown. He did simplify by assuming all crushdown occured first, and all crushdown occurred second. But his calculations could be modified to reflect other scenarios.

But it should also be noted that it is not valid to assume that the weaker or lighter part of the collision is always the one to break. One counterexample is when a karate black belt breaking bricks with his hand. This works because the energy transfer is mostly from the moving object to the stationary one. How much and why is a matter of calculation, not speculation, and that is exactly what engineering is about. If you think Bazant made a mistake, find it and redo the calculation correctly.

I suspect that dwightvw is talking about one of the following articles. The first one is an editorial from ENR that came out prior to the NIST report, and appears to be opposed to even researching the issue. And the collapses were called “rare” rather than “unique.”

The second article praises NIST profusely, agrees with the findings. but implies that no changes in building design are needed because it was the failure of the fire proection not the structural design itself). The extraordinary and rare thing that they are talking about is the stripping off of the fire protection by the impact of the jets.

Structural engineers have done wonders to help since the planes slammed into the New York City’s World Trade Center and Americans lost their innocence. The Structural Engineers Association of New York members worked around the clock at Ground Zero to advise rescue and cleanup workers as to the structural stability of the debris. Volunteers, numbering more than 300, risked their lives to keep others safe. And SEAoNY currently is trying to raise funds to produce a book to give firefighters information about the structure and layout of each of the 1,000-plus New York City buildings 20 stories or taller, which could save lives in future fires.

But there are some who are trying to take advantage of the “window of opportunity” created by the 9/11 terrorist attacks to do research for research’s sake. They are pressing their initiatives before the window closes, without having first demonstrated a need for action. This is what appears to be happening with the initiative to develop codes and standards to prevent progressive collapse.

At a recent workshop on progressive collapses, just about all the experts gathered could agree upon was that the World Trade Center failures do not qualify as progressive collapses under the accepted definition. But the leaders of the initiative are calling for action under the guise of 9/11 and of protecting national security. There is little that a progressive collapse standard as applied to commercial buildings could do to protect national security. Before taxpayer dollars are spent mitigating a rare mode of building failure, it is critical to establish that lives and property are at risk. This has not been well demonstrated to date.

No surprises in the results of federal probe into collapse of the twin 110-story towers

Structural and fire experts are gratified but not surprised by the latest “interim” findings of the National Institute of Standards and Technology on the behavior of the World Trade Center’s twin 110-story towers after the buildings were attacked by terrorists on Sept. 11, 2001. NIST has concluded, after completing most of its in-depth, $16-million investigation, that the towers would likely have withstood the heat of the jet-fuel-triggered fires had the hijacked planes and the debris from impact not knocked off the sprayed-on fireproofing.

Building design professionals are also not surprised by NIST’s “working hypothesis” that the frames’ sprayed-on fireproofing was adequate to maintain the structural integrity of the steel tubes in an “ordinary” office fire that was not fought, but left to burn out.

“NIST confirmed what I, and others, have been saying for the past three years,” says Edward M. DePaola, principal of structural engineer Severud Associates, New York City, and a member of the first team that investigated the disaster. “It was the fire, not the structural damage or any perceived design deficiencies, that caused the collapse,” he says.

Shyam Sunder, Gaithersburg, Md.-based NIST’s lead WTC investigator, says the study, considered the most in-depth probe ever of a building disaster, is important because it provides documentation for what many knew all along.

Some sources think the entire exercise was a waste of taxpayer money. Richard C. Schulte, a fire protection engineer based in Evanston, Ill., has been strident in his criticism against those, including New York City-based Skyscraper Safety Campaign, who blame the 9/11 deaths on the structural integrity of the twin towers and their original designers and builders, rather than the terrorists (ENR 6/7 p. 48).

“NIST’s preliminary conclusions pretty much lay to rest the Skyscraper Safety Campaign’s allegations that the towers were improperly designed and constructed,” says Schulte.

James Quintiere, a professor in the Dept. of Fire Protection Engineering at the University of Maryland, College Park, and an advisor to the Skyscraper Safety Campaign, declined to comment on the preliminary conclusions other than to ask for “clear and convincing” evidence from NIST that “all the insulation was knocked off the core columns, since that is crucial to their conclusions.”

Engineers involved with other studies of the WTC destruction also are weighing in on the latest NIST reports. “We think that rigorous efforts like these, taking a year or more, are needed…to counteract the kind of rash judgments that immediately followed the events of 9/11,” says Najib N. Abboud, associate principal of Weidlinger Associates Inc. The New York City-based firm led a WTC probe sponsored by the WTC leaseholder, Silverstein Properties, which is among the firms being blamed for the WTC deaths in pending personal injury lawsuits. “Such premature judgments have misled victims’ families and unfairly besmirched the reputation of innocent parties,” adds Abboud.

The interim report, released Oct. 19, says the towers’ structural steel was stripped of its fireproofing by the impact of the hijacked planes and the debris from the crashes. The heat from the resulting fires eventually sapped the strength of the unprotected steel. Eventually, the towers collapsed. NIST determined the region of dislodged fireproofing from the predicted path of debris.

“Had the fireproofing not been dislodged, the temperature rise of the structural components would likely have been insufficient to cause the global collapse of the towers,” says NIST. “Fireproofing dislodged by debris left the components more sensitive to heat man any areas where mere was missing or thin fireproofing before the aircraft impacts.”

Adds Sunder: “If the sprinkler systems were not operational in multifloor fires, our current working hypothesis is that the buildings would not have collapsed.”

NIST has also determined that the majority of the WTC steel was stronger than minimum requirements. In recent fire tests, NIST found that the floor systems met the local building code of the time (ENR 9/13 p. 16).

NIST plans to release its draft for public comment by February. The final report’s release is expected in May. The final report on Seven WTC, which collapsed on 9/11 after burning unattended for seven hours, is expected in July.

Thanks, anonanonanon. I’ll keep looking to be sure, but that looks like the article I saw.

I stand by my reading — they don’t want NIST’s report to be the basis for structural code changes. But I see your argument and theirs — if the insulation had not been stripped, the collapse would not have started. Like NIST, they are not really answering what happened.

Look at this presentation which discusses various definitions of “progressive collapse.”

If these definitions are applied, the argument appears to be that the buildings were not damaged to an extent disproportionate to the original local damage, so it is not a “progressive collapse” needing to be addressed by changing design standards.

So the question is whether the damage was disproportionate. NIST did not address this, nor do the engineers, who are only arguing that codes don’t need to be changed. I am convinced both that initial collapse would not have ensued, and that even if it had, the entire building would not have come done. I don’t see any concern about overstating this, especially the latter. It’s basic physics.

(An aside: I’ve decided to speak with the same conviction of Matthew Rothschild, Alexander Cockburn, Chip Berlet, and Robert Scheer, who use words like “nuts,” “crackpot,” and “inane” to describe 9/11 “conspiracy theories.” The difference is, I have a basis for my conviction because I have addressed the facts. I shall also use this same conviction in addressing Bazant’s patently absurd, and thus fraudulent, “theory.” I think it’s far past time for 9/11 activists to quit being mealy mouthed in their conviction that the buildings were demolished, because it is completely obvious and has been since the morning of 9/11.)

Well, I guess that depends on who your target audience is. My target audience, for my posts on technical matters at least, is scientists, engineers, other scholars, and other highly educated, thinking people. With that crowd, it is far better be responsibly cautious, avoid jumping to conclusions, avoid overstatement, and be civil to everyone.

Furthermore, my aim is to build a genuinely strong case. To that end, it is necessary to examine the issues from all sides, to weed out the weaker arguments.

Denouncing the OCT defenders as “crackpots” (or whatever) may be emotionally satisfying, but it will not help us build a stronger case.

“But it should also be noted that it is not valid to assume that the weaker or lighter part of the collision is always the one to break.”

But it did. That is clear in the videos. Yet Bazant assumes it does not.

“One counterexample is when a karate black belt breaking bricks with his hand. This works because the energy transfer is mostly from the moving object to the stationary one. How much and why is a matter of calculation, not speculation, and that is exactly what engineering is about. If you think Bazant made a mistake, find it and redo the calculation correctly.”

Bazant assumed instant, complete, and symmetrical removal of at least one floor. That’s a big assumption — good for his theory, perhaps, but not real world. And he doesn’t explain how the top of the building drives down through 80-90 thicker floors. He doesn’t explain holw it could do that without damage, and he doesn’t explain how it could do that if it were damaged, which the videos show it was.

Karate chops work because the bone is stronger than the object being hit, the blow is concentrated in a small error, and also, perhaps, because the pulling away rather than following through allows full oscillation of the object.

It’s not a matter of “emotional satisfaction.” It’s a matter of not spinning our wheels debating with people who make absurd arguments, which gives the impression that the issue is debatable. It’s not. The case was made years ago and it’s long been time to state that with conviction.

I imagine Robert Scheer, Alexander Cockburn, and Maththew Rothschild also consider their audiences to be highly educated, reasonable people, yet they have no problem throwing around words like “nuts” and “inane,” with no argument other than that an institution has endorsed a theory. And this from supposed progressives who say that “conspiracists” lack structural understanding of how institutions work.

I’m highly educated and thinking, and I know how obfuscation works. Simple is not wrong, and complicating things is a way to cover for core fallacies. I don’t need an engineering degree to understand basic physics.

Swightvw:
I’m highly educated and thinking, and I know how obfuscation works. Simple is not wrong, and complicating things is a way to cover for core fallacies. I don’t need an engineering degree to understand basic physics.

Seems like I can’t make it any simpler than what I said before. “If you think Bazant made a mistake, find it and redo the calculation correctly.”

In comment #20, you quoted Behind the Collapse, PBS, May 1, 2002. Thanks for posting this. Very interesting quotes from Tom Bearden, David Childs, and Jonathan Barnett. If nothing else, this article is good counterevidence against the claim, which I’ve seen elsewhere, that all engineers expected the towers to fall. For that matter, even Bazant’s latest paper, if I recall correctly, admits that the fall of the towers was a surprise.

The “error” is manifest – it speaks for itself. Bazant’s theory not only does not account for what was observed, it is self-contradictory. Once the crushup starts, why would it stop when it got to higher and weaker floors?

During the initial crush-up, the collapsing top part accelerated downward. If indeed Bazant’s model is otherwise correct (which I strongly doubt), then the downward acceleration of the top part eventually, after a few floors’ worth of crush-up, would have given the top part enough momentum and kinetic energy to break the floor below, starting the crush-down.

Why would the crushed material not be expelled laterally, at least in part, as the building moved down during the crush up stage?

Some of it was expelled laterally, but not all of it. I’m not sure how to estimate the portion that was expelled laterally. If the amount that was expelled laterally is less than one floor’s worth per floor of descent, then the total mass of the descending rubble pile would increase on the way down.

As noted in one of my many parenthesized P.S.’s to the above post, Bazant’s hypothesis does seem to me intuitive unlikely, based on, among other things, the sheer thickness of the core columns in the lower and middle parts of the building, as seen in this construction photo, for example. But actually disproving Bazant’s hypothesis requires more than intuition (which is sometimes wrong, especially on matters outside our everyday experience). It will require some quantitative analysis.

Diane, I don’t disagree with what you are saying here, but I was trying to suggest to you how to quantify your question. I am suggesting you can use a mass flux approach, where the mass hitting a given floor is estimated by looking at how much mass would pass through an imaginary plane sitting an infintesimal distance above the floor and equal in size to the area of the floor. This would give you the amount of material hitting the floor per unit time. You can estimate this by guessing how much a broken up floor might spread as it falls to the floor below.

I also speculated that this wouldn’t make much difference in bazant’s calculations, but you can pretty much ignore that speculation since I haven’t done this calculation myself.

The nice thing about Bazant’s paper is that he gives you an equation that describes everything, and then plugs in calculations to estimate all the parameters. It wouldn’t be hard to alter his model to reflect a difference sequence of crush up and crush down, or different assumptions about the force bearing down on the building etc.

Thanks for the suggestion. Unfortunately, I don’t think I have the background to do all the necessary calculations myself. Perhaps one of the structural engineers in Architects and Engineers for 9/11 Truth might be able to help me with this.

We have an ongoing post going on about 911 on Suzi-Q’ blog with Arthur Scheuerman posting about his contention that fire brought all three buildings down. Of course in the real world the chances of this happening would be like a fart in a tornado. There is overwhelming evidence that the buildings were demolished and there is every reason to initiate a new investigation asap…G:

“If indeed Bazant’s model is otherwise correct (which I strongly doubt), then the downward acceleration of the top part eventually, after a few floors’ worth of crush-up, would have given the top part enough momentum and kinetic energy to break the floor below, starting the crush-down.”

No, the crushup would continue as the floors get weaker going up. Even if the floor that was the base against which the crushup occurred began to collapse from all this impact, why would this start a process that continues all the way to the ground? The process would fizzle out, most likely not with crushup, but with the block falling off the side. Bazant claims, or assumes, a perfectly symmetrical free fall drop over at least one floor, or more likely 3-10 floors. Why would this occur? Even if a perfectly symmetrical collapse occurred, why can it be equated to a free fall drop as if one floor magically disappears? And since the fires were assymetrical, how can he assume a symmetrical flat drop rather than an angular drop?

We are arguing nonsense, really. Bazant claims the top part of the building fell straight down through the much more massive building below, nearly as fast as through air. Pigs sooner fly.

The post linked below is a reply to an article by Petros Evdokas, “Demolition is an understatement,” commenting about a discussion in the Truth Action forum about the post here on this page about Demolition of the WTC. Links to parts of Petros Evdokas’s original article can be found in his comment above.